Current electronic fluid level sensing technology generally includes two types: discrete level and analog level. Discrete level type sensors return one or several electrical signals indicating when a monitored fluid reaches one or several predetermined levels. The analog level type sensors return a single electrical signal that correlates to the fluid level within a range of fluid levels. The analog signal may be a current or a voltage that varies with fluid level.
Generally, analog fluid sensors are more complicated and expensive than discrete level sensors because of the electronics necessary. Some common electronic technologies for analog fluid sensors include capacitive sensors to measure the electric field flux variations imposed by proximal fluid, and ultrasonic sensors that measure sonic echo delays varied by fluid surface distances. Discrete level sensing technology often uses a float and a switch or a float with a magnet and one or more small magnetic switches along the path of the float. “Level sensor” on Wikipedia offers an in-depth discussion of current fluid level sensor types and how they work. For example, level sensors detect the level of substances that flow, including liquids, slurries, granular materials, and powders. Fluids and fluidized solids flow to become essentially level in their containers (or other physical boundaries) because of gravity whereas most bulk solids pile at an angle of repose to a peak. The substance to be measured can be inside a container or can be in its natural form (e.g., a river or a lake). The level measurement can be either continuous or point values. Continuous level sensors measure levels within a specified range and determine the exact amount of substance in a certain place, while point-level sensors only indicate whether the substance is above or below the sensing point. Generally the latter detect levels that are excessively high or low.
The electronics are usually chemically and electrically isolated from the fluid whose level is to be measured. Sometimes, greater accuracy imposes higher demands on the isolation and mechanics, which can also lead to higher costs and more complex solutions.